The present invention generally relates to minimally invasive surgery. In particular, the present invention relates to percutaneous translumenal minimally invasive coronary surgery.
Coronary arteries can become partially restricted (stenotic) or completely clogged (occluded) with plaque, thrombus, or the like. This reduces the efficiency of the heart, and can ultimately lead to a heart attack. Thus, a number of different systems and methods have been developed for treating stenotic or occluded coronary arteries.
Two methods which have been developed to treat occlusions and stenosis include balloon angioplasty and pharmacological treatment. However, where the occlusion is quite hard, it can be quite difficult, if not impossible, to cross the occlusion with an angioplasty device. In addition, some coronary stenosis are to diffuse to treat effectively with balloon angioplasty. Unfortunately, such occlusions are not readily susceptible to dissolution with chemicals either. In the past, patients with these types of occlusions have been candidates for open heart surgery to bypass the restrictions.
However, open heart surgery includes a myriad of disadvantages. Open heart surgery typically includes a great deal of postoperative pain. The pain is normally encountered because conventional open heart surgery requires that the sternum be cracked open, which is quite painful. Also, open heart surgery typically involves bypassing the occluded vessel, which, in turn, involves harvesting a vein from another part of the body for use as the bypass graft. One common source for the bypass graft is the saphenous vein which is removed from the leg. Harvesting the saphenous vein requires the surgeon to cut and peel the skin back from an area of the leg which is approximately 18 inches long and which extends upward to the groin area. This can be very traumatic and painful. Further, open heart surgery requires quite a lengthy recovery period which involves an increased hospital stay, and, consequently, greater expense.
Other than the pain and more lengthy hospital stay, open heart surgery involves other disadvantages as well. For example, during open heart surgery, it is common to cool the heart to a point where it stops. The blood from the remainder of the vasculature is then pumped through a pulmonary and cardiac bypass system. Any time the heart is stopped, there is a danger of encountering difficulty in restarting the heart (which is typically accomplished by warming the heart and massaging it). Further, even if the heart is restarted, it sometimes does not return to a correct rhythm. Also, open heart surgery can require the use of a device known as a left ventricular assist device (LVAD) to supplementarily pump blood to relieve the burden on the heart. This allows the heart to heal.
A significant reason that the heart is typically stopped during open heart surgery is that, if it were not stopped, the surgeon would be working in a dynamic environment. In such an environment, the target vessels and tissue to be treated are moving. Further, a system must be employed in such an environment to stop bleeding. Clinical studies indicate that, when blood flow is stopped using clamping devices and blood flow is diverted to a cardiac bypass system, a statistically significant instance of neurological problems caused by blood clotting results. The use of mechanical clamps to stop blood flow, and the use of a mechanical bypass system, results in an approximate six percent instance of neurological problems, such as stroke, memory failure, etc.
Given the difficulties of the techniques discussed above, another approach has been developed which does not require stoppage of the heart or an open chest during execution. This approach is to perform a bypass using a minimally invasive technique by entering the upper chest cavity, through a hole between ribs under visual observation. Such a technique is often referred to as minimally invasive direct coronary artery bypass (MIDCAB) (where the heart is not stopped). or heart port (where the heart is stopped). Such a system which is used to perform a bypass is disclosed in the Sterman et al. U.S. Pat. No. 5,452,733.
Yet another approach has been developed which does not require stoppage of the heart or an open chest. This alternative approach is even less invasive than the MIDCAB approach because it does not require accessing the upper chest cavity through a hole between the ribs.
In particular, this alternative approach, which may be referred to as percutaneous translumenal minimally invasive coronary surgery, involves accessing the coronary vasculature from within the vasculature of the body. For example, a percutaneous translumenal approach may involve accessing the femoral artery in the groin region and advancing a suitable device to the coronary arteries by way of the aorta. Once in the coronary vasculature, the restriction may be bypassed by exiting the coronary artery proximal of the restriction and defining an alternative fluid path to the coronary artery distal of the restriction. An example of this approach is disclosed in International Application No. PCT/US96/16483.
The present invention provides several devices and methods for performing percutaneous translumenal minimally invasive coronary surgery, particularly bypass surgery. Specifically, the present invention permits a physician to perform percutaneous bypass surgery involving one or more of the following basic steps: determining a proper location for treatment, navigating a suitable catheter to the treatment site, creating an extravascular opening and pathway, monitoring the progress of creating the opening and pathway, and maintaining the extravascular opening and pathway. One or more extravascular openings and/or pathways may be created to define a fluid path or bypass around the vascular restriction. Several devices and methods are included in the present invention for performing one or more of these steps. Those skilled in the art will recognize that the devices of the present invention may be modified (e.g., combined or separated) to perform singular functions or multiple functions without departing from the scope and spirit of the present invention.
The extravascular opening may be any or a combination of the following: an arterial entry or reentry, an arterial exit, a venous entry or re-entry, and/or a venous exit. The pathway may be established external to the heart muscle (e.g., the pericardial space), internal to the heart muscle (e.g., the myocardium), and/or in the case of adjacent vessels, the pathway may be defined by the openings in the vascular wall(s).
One embodiment of the present invention provides an intravascular catheter for creating an extravascular opening in a vessel wall. The catheter includes an elongate shaft adapted for intravascular navigation, an anchoring mechanism disposed on the distal end of the shaft, and a tissue penetrating member having a proximal end slidably disposed in the shaft of the catheter and a distal end including a tissue penetrating mechanism. The tissue penetrating member is extendable between a retracted position and penetrating position wherein the tissue penetrating mechanism extends completely through the vessel wall to establish an extravascular opening therethrough. The catheter may include a stiffening member slidably disposed about the tissue penetrating member for providing rigidity to the distal portion.
The anchoring mechanism may comprise, for example, an inflatable balloon that is deflated in the delivery position and inflated in the anchoring position. The distal end of the tissue penetrating member may exit the shaft proximal or distal of the anchoring mechanism, or the tissue penetrating member may exit the anchoring mechanism.
Another embodiment of the present invention provides a method of bypassing a restriction in a vessel using an intravascular catheter having a tissue penetrating member. The method involves initially retracting the tissue penetrating member into the catheter such that the tissue penetrating mechanism is retracted inside the catheter (this may be done by the treating physician or by the manufacturer of the catheter). The catheter is then translumenally navigated to the treatment site, preferably to a position adjacent the restriction, typically an arterial restriction. The tissue penetrating member is then actuated such that it penetrates completely through the wall of the vessel to establish an extravascular opening. The tissue penetrating member may be further actuated to establish a pathway. The tissue penetrating member is then retracted inside the catheter and the catheter may be withdrawn.
The catheter may include an anchor mechanism that is actuated prior to actuating the tissue penetrating member. Preferably, the anchor mechanism is anchored adjacent the restriction in the vessel. If the anchor mechanism is a balloon, the anchor mechanism may be actuated by inflating the balloon.
The step of creating an extravascular opening and pathway may be monitored by injecting radiopaque contrast media into the penetrating member, observing the penetrating member under fluoroscopy as it penetrates the wall of the vessel, and retracting the penetrating member when contrast media is observed exiting the distal end of the penetrating member into an adjacent vessel.
Alternatively, the step of creating an extravascular opening and pathway may be monitored by emitting light from the distal end of the penetrating member, detecting light reflected by tissue adjacent the distal end of the penetrating member, and retracting the penetrating member when the reflected light indicates that the penetrating member is in a lumen in an adjacent vessel.
A further alternative of monitoring the step of creating an extravascular opening and pathway is by emitting light from the distal end of the penetrating member, detecting light emitted from the distal end of the penetrating member in a lumen of an adjacent vessel, and retracting the penetrating member when the detected light indicates that the penetrating member is in the lumen of the adjacent vessel.
Yet a further alternative of monitoring the step of creating an extravascular opening and pathway is by measuring pressure at the distal end of the penetrating member, observing the pressure as the penetrating member penetrates the wall of the vessel, and retracting the penetrating member when the pressure indicates that the penetrating member is in a lumen of an adjacent vessel.
The step of creating an extravascular opening and pathway may also be monitored utilizing intravascular ultrasound devices and techniques.
The extravascular opening may be modified (e.g., enlarged) to accommodate a means to maintain the opening and pathway, such as a stent or graft. For example, a dilator may be navigated to the opening and used to enlarge the opening. The dilator may be rotated as it enlarges the opening in order to reduce friction.
The extravascular opening and pathway may be maintained by providing a stent or graft and positioning the stent or graft in the opening and pathway. Alternatively, the opening and pathway may be maintained by providing a thermal energy emitter for heat fusing the tissue defining the opening and pathway. If the thermal energy emitter comprises a heatable balloon, the balloon may be inflated and activated so as to heat the tissue surrounding the opening and pathway.